I’d say the big issue is the amount of Supreme Court decisions that are essentially laws that don’t exist

I wonder how much damage it would do to the US letting the policymakers of today draft up a new constitution. I wonder how different it would be.

Overturning Marbury would turn the Supreme Court into a court of review, meaning they only apply the law as written.

This is correct as to what SCOTUS can pass final judgement upon. What would be unaffected would be theirs powers in equity, which show up prominently when it comes to preliminary injunctions. So in a world without Marbury, a lawsuit against the federal government challenging the constitutionality of a particular law could not proceed, because SCOTUS (and by extension, all inferior federal courts) wouldn't be able to rule on that question.

But if instead, a lawsuit challenges whether the federal government followed the procedures defined in law, or if there is ambiguity as to how the law might be interpreted, then SCOTUS would still have the power to intervene while the case progresses -- which would typically restore the status quo, but the current SCOTUS seems allergic to that -- and then could pass judgement in law on how a statute is read, or in equity on how ambiguity is resolved. Litigants would change their tactics to adapt to this environment.

This is part for core, raw power that the court retains, even without Marbury: it can, at great reputational cost, read a statute that says "no parking on Tuesday" to mean any of: 1) no parking on any Tuesday of any week, 2) no parking on only the Tuesday following the passage of the statute, and then parking is always permitted thereafter, 3) parking of automobiles is banned nationwide, but only in National Parks because of their "uniquely structured, quasi-private entity with a distinct historical tradition", even when this openly contradicts history.

The power to say what words mean is awe-inducing but also terrifying, one that can maintain good governance but can also turn into an Orwellian double-plus bad nightmare.

Ahh good point. So would be against their personal interests to repeal it this way

I think there's enough precedent at this point that everyone would still treat the Construction as law.

What construction?

I'm surprised that the Constitution didn't come with a mechanism of enforcing compliance to itself built in. Many other countries, whose founders had the luxury of hindsight, have a constitutional court for exactly this purpose written into their constitution.